Patent GB-1112872-A (GB)
Title: Improvements in or relating to the cold separation of gas mixtures
IPC: B01D3/14
Filed: 1966-07-26
Abstract: 1,112,872. Cold separation of gas mixtures. LINDE A.G. 26 July, 1966 [28 July, 1965], No. 33562/66. Heading F4P. Separation of a gas mixture containing at least two constituents of widely differing boiling points, e.g., a mixture of ethane and ethylene containing 10 to 20 per cent methane, is effected by feeding liquefied mixture into the head of a rectification column 2, Fig. 1, withdrawing methane-enriched vapour from the head and passing it through a line 5 to a further separation step e.g., switchable regenerators 6, 7, 8 in which C 2  hydrocarbons are  condensed and subsequently re-vaporized and returned through a line 10 to the mid-point of column 2 whilst product gaseous methane is withdrawn through a line 13. Pure methane leaving the warm end of the on-stream regenerator 6 is expanded in a turbine 9 and divided into a first portion which revaporizes C 2  hydrocarbon deposited in a previous cycle in regenerator 7 and is then returned by a compressor 12 through line 10 to column 2 and into a second portion which cools the regenerator 8. Column 2 is heated by gaseous ethylene being condensed in a coil 3 and liquid C 2  hydrocarbons are withdrawn through a line 4. In a modification the further separation is effected in a dephlegmator 15, Fig. 2, cooled by downward reverse flow of purified methane having been expanded in a turbine 9; the separated hydrocarbon liquid being expanded in a valve 16 and passed through a line 17 to the compressor 12 and line 10 leading to the midpoint of column 2, whilst product gaseous methane is withdrawn through a line 14. In a further modification the further separation is effected in interchangeable absorbers (19, 20), Fig. 3 (not shown), whilst in a still further modification the further separation is effected by scrubbing at 26, Fig. 4, with liquid propane, withdrawing produce methane through a line 29, forcing liquid C 2  hydrocarbons from the base of scrubber 26 by a pump 30 into a stripping column 27 thereby separating the C 2  hydrocarbons which are returned through a line 28 to the mid-point of column 2 and propane which is forced by a pump 34 to the head of scrubber 26. In separating C 4  and C 5  hydrocarbons from methane leaving the head of column 2 two dephlegmators (36, 40), Fig. 5 (not shown), are used in series, the bottom liquid from each being returned to the midpoint of column 2. Fig. 7 (not shown) shows apparatus for separating methane, ethane, propane and butane wherein overhead from the first rectification column (54) is fed to a dephlegmator (49) from which liquid methane and ethane is fed through a line (66) to a second rectification column (67). Product liquid ethane is withdrawn through a line (69) and methanerich overhead gas is passed through a line (71) to a second dephlegmator (72) from which product methane is withdrawn through a line (75) and from which liquid ethane is withdrawn through a line 78, expanded at (76) revaporized at (79) and forced by a compressor (80) through an evaporator-condenser (82) into the mid-point of column (67). Liquid C 2  hydrocarbons from the base of column (67) and from the base of dephlegmator (59) are returned to the mid-point of column (54).